1. Field of the Invention
The present invention relates to a DC/DC voltage converter and, more particularly, to a buck-boost voltage converter capable of generating a regulated output voltage from an input voltage, which may be larger than, equal to, or smaller than the output voltage.
2. Description of the Related Art
DC/DC voltage converters transform an input voltage into a regulated output voltage and supply a current required by an external load at such a regulated voltage. A variety of portable electronics systems like digital cameras, disc players, laptop computers, and mobile phones employ some kind of voltage converters as a supply of controllable, regulated power. Typically, batteries are used for the input voltage by the portable electronics systems. After a long time use of the battery, the voltage provided across the battery will drop. It is possible that at the beginning the battery voltage is much higher than the output voltage to be regulated but after continuously supplying energy the battery voltage becomes almost equal to the output voltage to be regulated. If in such situation the voltage converter can still generate the regulated output voltage, the life of the battery is successfully prolonged.
If the battery keeps on duty, it should be expected that the battery voltage continues to drop and eventually becomes lower than the output voltage to be regulated. Even in this situation, if the voltage converter can still generate the regulated output voltage, the life of the battery may be prolonged to its longest possibility. Therefore, it is desired to develop a buck-boost voltage converter capable of generating a regulated output voltage from an input voltage, which may be larger than, equal to, or smaller than the output voltage.